Description of the Prior Art
Canine pet foods do not provide sufficient surface cleaning, exercise and massage to the teeth and gums of pets for optimum health. Rawhide dog chews in the form of knotted strips and other shapes have been used to satisfy these needs. The rawhide dog chews are expensive, rawhide supplies being limited, and the indigestible leather fragments swallowed by the dogs are constipating and have essentially no nutritional value.
Extruded oil seed protein products have been processed in many ways to produce products resembling meat. For example, alkaline and other special pH treatment to solubilize proteins prior to formation of protein products have been described in U.S. Pat. Nos. 3,440,054, 3,800,053 and 4,125,630. In general, pH treatment increases the amount of water-soluble protein facilitating the shaping process and providing products having a final texture resembling meat. In preparing the simulated food products, the oil seed protein is treated under heat and pressure with mechanical working and is extruded through a shaping orifice. The use of plasticizers such a glycerol to facilitate the working and extrusion has been disclosed in U.S. Pat. No. 3,891,774. Use of triglycerides and lecithin is discussed in U.S. Pat. No. 4,125,630. Procedures for converting oil seed proteins alone or in combination with other proteins to an extrudable mass solely with heat, pressure and mechanical working have been described for preparing simulated meat products. In the procedures described in U.S. Pat. Nos. 3,488,770, 3,904,769, 3,978,236, and 4,216,240, the plasticized oil seed composition is extruded at a temperature above the boiling point of water, causing steam formation and expansion in the form of fine bubbles in the extruded protein. This "puffed" product is described as having physical properties more closely resembling meat.
U.S. Pat. No. 3,925,566 is directed to a process for preparing a puffed oil seed protein product resembling meat wherein the oil seed protein, water and other additives are worked under substantial heat and pressure to form an extrudable mass, and the mass is cooled in the extruder die prior to its exit into the atmosphere so as to prevent puffing. The product is a translucent, glassy product. This product is subsequently treated by soaking it in water at temperatures above 100.degree. C. and pressures above atmospheric pressure and then releasing the pressure suddenly to cause puffing, expanding the product tenfold or more in volume.
A review of the state of the art of processing soy proteins to make fabricated foods is presented in FABRICATED FOOD, G.E. Ingledt, pp. 49-67 (1975).